How do I know my 3yo is getting all the essentials nutrients and is a super healthy child?

Personally, I have followed only one thing, which is, if my child is active as one should be her age, I know she is healthy. There have been days and visits to relatives' place where someone or the other makes it a point to say that she has become weak. So, I listen to them and ignore because I know, these are mandatory things to say in our society when they meet people. I think, feed your child all seasonal fruits, veggies, meat, nuts, dairy products like; curd, milk, ghee and fresh juices, little tidbits of what kid wants, and once in a while chocolates, ice-cream and he would do fine. Check this link: http://www.webmd.com/parenting/features/4-nutrients-your-child-may-be-missing